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Randomized cell modeling for calculating the contractile force of cardiomyocyte
Hojae Bae,Sungwook Yang,Kyounghwan Na,Eui-Sung Yoon,Jinseok Kim 대한전자공학회 2009 ITC-CSCC :International Technical Conference on Ci Vol.2009 No.7
Real-time monitoring of the magnitude and frequency of cardiomyocyte contraction is one of the most important methods for the toxicity of chemicals on cardiomyocyte and for understanding of the mechanisms of heart failure. The randomized cell approximation was introduced to model the hybrid biopolymer structure applying cell distribution close to the actual distribution.
Carbon Nanotube Reinforced Hybrid Microgels as Scaffold Materials for Cell Encapsulation
Shin, Su Ryon,Bae, Hojae,Cha, Jae Min,Mun, Ji Young,Chen, Ying-Chieh,Tekin, Halil,Shin, Hyeongho,Farshchi, Saeed,Dokmeci, Mehmet R.,Tang, Shirley,Khademhosseini, Ali American Chemical Society 2012 ACS NANO Vol.6 No.1
<P>Hydrogels that mimic biological extracellular matrix (ECM) can provide cells with mechanical support and signaling cues to regulate their behavior. However, despite the ability of hydrogels to generate artificial ECM that can modulate cellular behavior, they often lack the mechanical strength needed for many tissue constructs. Here, we present reinforced CNT–gelatin methacrylate (GelMA) hybrid as a biocompatible, cell-responsive hydrogel platform for creating cell-laden three-dimensional (3D) constructs. The addition of carbon nanotubes (CNTs) successfully reinforced GelMA hydrogels without decreasing their porosity or inhibiting cell growth. The CNT–GelMA hybrids were also photopatternable allowing for easy fabrication of microscale structures without harsh processes. NIH-3T3 cells and human mesenchymal stem cells (hMSCs) readily spread and proliferated after encapsulation in CNT–GelMA hybrid microgels. By controlling the amount of CNTs incorporated into the GelMA hydrogel system, we demonstrated that the mechanical properties of the hybrid material can be tuned making it suitable for various tissue engineering applications. Furthermore, due to the high pattern fidelity and resolution of CNT incorporated GelMA, it can be used for <I>in vitro</I> cell studies or fabricating complex 3D biomimetic tissue-like structures.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2012/ancac3.2012.6.issue-1/nn203711s/production/images/medium/nn-2011-03711s_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn203711s'>ACS Electronic Supporting Info</A></P>
주파수영역 독립성분분석을 이용한 수동소나 표적신호 분리
이호재,서익수,배건성,Lee, Hojae,Seo, Iksu,Bae, Keunsung 한국음향학회 2016 韓國音響學會誌 Vol.35 No.2
수동소나 시스템에서는 함정의 소음원에서 발생하는 방사 소음을 분석하여 표적을 탐지 및 식별한다. 소나의 탐지 범위 안에 다수의 소음원이 존재하면 신호를 분석할 때 각 소음원에서 나오는 성분들이 혼합되어 각각의 소음원을 규명하기가 어렵다. 이를 해결하기 위해 일반적으로는 배열 센서를 이용한 빔을 형성하여 소음원의 신호를 공간적으로 분리하는 기법이 사용되지만 환경에 따라 여전히 어려운 점이 있다. 본 연구에서는 수동소나 표적신호를 분리하기 위한 새로운 방법으로 주파수영역 독립성분분석(FDICA: Frequency Domain Independent Component Analysis)을 적용하고, 혼합된 표적신호를 분리하는 모의실험을 수행하여 그 타당성을 검증하였다. 표적신호 합성을 위한 특징 정보로는 기계류 토널 성분 및 프로펠러 성분을 사용하였고, 분리 전 후의 결과를 LOFAR(Low Frequency Analysis and Recording), DEMON(Detection Envelope Modulation On Noise) 분석을 통해 비교하였다. Passive sonar systems detect and classify the target by analyzing the radiated noises from vessels. If multiple noise sources exist within the sonar detection range, it gets difficult to classify each noise source because mixture of noise sources are observed. To overcome this problem, a beamforming technique is used to separate noise sources spatially though it has various limitations. In this paper, we propose a new method that uses a FDICA (Frequency Domain Independent Component Analysis) to separate noise sources from the mixture. For experiments, each noise source signal was synthesized by considering the features such as machinery tonal components and propeller tonal components. And the results of before and after separation were compared by using LOFAR (Low Frequency Analysis and Recording), DEMON (Detection Envelope Modulation On Noise) analysis.
Kim, Hyun Woo,Bae, Hojae,Park, Hyun Jin Elsevier 2018 Journal of food engineering Vol.220 No.-
<P><B>Abstract</B></P> <P>The printability of materials used in extrusion based 3D printing is one of the most important properties especially when fabricating objects with architectural complexities. However, this parameter is influenced by several factors (temperature, components, and additives) which makes thorough evaluation and classification challenging. In this study, the printability of food-ink for 3D food printing applications was evaluated by systematically adapting evaluation techniques such as dimensional stability test, handling properties assessment, and shear rheology test using edible hydrocolloid as reference materials. Methylcellulose (MC) was selected as a suitable reference material for its capability to simulate the printability of various types of food applications. In dimensional stability test, the concentrations of reference hydrocolloid mixture that could fabricate structures with height of 20, 40, and 80 mm without significant collapse were 9%, 11%, and 13%, respectively. The deformation behavior and handling properties of printed foods were classified based on the reference material produced at various concentrations (5%–20%). Shear modulus of all samples were in complete agreement with simulation results based on the dimensional stability test indicating that the printability of foods can be predicted and classified by comparing its properties to reference material. The newly established classification system of printability was categorized into grades A, B, C, and D according to the dimensional stability and degree of handling. The validity of this classification system was verified by 3D-printing tests.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Hydrocolloids was used as a reference material to simulate the printability of various types of food applications. </LI> <LI> The deformation behavior and handling properties of selected food were classified based on the reference material. </LI> <LI> A printability classification system was established based on the capability in dimensional stability and degree of handling. </LI> </UL> </P>
Benchtop fabrication of PDMS microstructures by an unconventional photolithographic method
Hwang, Chang Mo,Sim, Woo Young,Lee, Seung Hwan,Foudeh, Amir M,Bae, Hojae,Lee, Sang-Hoon,Khademhosseini, Ali IOP Pub 2010 Biofabrication Vol.2 No.4
<P>Poly(dimethylsiloxane) (PDMS) microstructures have been widely used in bio-microelectromechanical systems (bio-MEMS) for various types of analytical, diagnostic and therapeutic applications. However, PDMS-based soft lithographic techniques still use conventional microfabrication processes to generate a master mold, which requires access to clean room facilities and costly equipment. With the increasing use of these systems in various fields, the development of benchtop systems for fabricating microdevices is emerging as an important challenge in their widespread use. Here we demonstrate a simple, low-cost and rapid method to fabricate PDMS microstructures by using micropatterned poly(ethylene glycol) diacrylate (PEGDA) master molds. In this method, PEGDA microstructures were patterned on a glass substrate by photolithography under ambient conditions and by using simple tools. The resulting PEGDA structures were subsequently used to generate PDMS microstructures by standard molding in a reproducible and repeatable manner. The thickness of the PEGDA microstructures was controllable from 15 to 300 µm by using commonly available spacer materials. We also demonstrate the use of this method to fabricate microfluidic channels capable of generating concentration gradients. In addition, we fabricated PEGDA microstructures by photolithography from the light generated from commonly available laminar cell culture hood. These data suggest that this approach could be beneficial for fabricating low-cost PDMS-based microdevices in resource limited settings.</P>
Siphon-driven microfluidic passive pump with a yarn flow resistance controller.
Jeong, Gi Seok,Oh, Jonghyun,Kim, Sang Bok,Dokmeci, Mehmet Remzi,Bae, Hojae,Lee, Sang-Hoon,Khademhosseini, Ali Royal Society of Chemistry 2014 Lab on a chip Vol.14 No.21
<P>Precise control of media delivery to cells in microfluidic systems in a simple and efficient manner is a challenge for a number of cell-based applications. Conventional syringe pumps can deliver culture media into microfluidic devices at precisely controlled flow rates, but they are bulky and require a power source. On the other hand, passive microflow-generating systems cannot maintain continuous, controllable and long-term delivery of media. We have developed an on-chip microflow control technology that combines flow rate control and passive, long-term delivery of media to microwell tissue culture chambers. Here, a passive flow is initiated using the siphon effect and a yarn flow resistor is used to regulate the flow rate in the microchannel. Using the yarn flow resistor, the medium flow rate into the microfluidic cell culture system is made adjustable to a few hundred microliters per hour. To evaluate the effects of controlled flow on microfluidic cell culture properties (feasibility test), we measured the cell alignment and cytoskeletal arrangement of endothelial cells cultured in a microwell array inside the microfluidic channel.</P>